1. Field of the Invention
The present invention relates to a pressure sensor device for detecting the pressure of an object to be measured, and more particularly to a pressure sensor device which is combined with a temperature sensor for also detecting the temperature of the measured object.
2. Description of the Related Art
FIG. 5 is a sectional view of a conventional pressure sensor device disclosed in, e.g., Japanese Unexamined Patent Publication No. 6-281519. In FIG. 5, a pressure sensor 1 is mounted on a circuit board 2 such that leads 1a projecting from one side of the pressure sensor 1 are soldered to the circuit board 2. A pressure reference chamber (not shown) is air-tightly formed inside the pressure sensor 1. A pressure detecting element (not shown) which also air-tightly forms a pressure introducing chamber is disposed in the pressure reference chamber. A pipe 1b extending out of the pressure sensor 1 is connected to the pressure introducing chamber. The pipe 1b introduces the pressure of an object to be measured, e.g., air, to the pressure introducing chamber. The pressure detecting element is deformed depending on a pressure difference between the pressure introducing chamber and the pressure reference chamber. An amount of the resulting deformation is converted into an electrical signal indicating the pressure of the measured object and is then output to the exterior through the leads 1a.
The pressure sensor 1 is mounted on the circuit board 2 with the pipe 1b penetrating a through hole 2a bored in the circuit board 2. Above the circuit board 2, there is another ceramic circuit board 2c being U-shaped in section and disposed to cover the pressure sensor 1. Output terminals 3 for delivering an output signal of the pressure sensor 1 to the exterior are extended from one end of the circuit board 2. An assembly of the circuit board 2 and the pressure sensor 1 is placed on a base 4 with an outer peripheral portion of the circuit board 2 supported by the base 4, and is further covered by a resin-made, box-shaped housing 5. Both the base 4 and the housing 5 jointly constitute a sensor container 6 for containing the above assembly.
The pressure sensor 1 and the ceramic circuit board 2c are installed in a space defined by the base 4 and the housing 5, i.e., an inner space of the sensor container 6, in such a state as not contacting the container. Between the housing 5 and the ceramic circuit board 2c, a box-shaped shield cover 5b is disposed so as to cover the ceramic circuit board 2c. A peripheral edge of the shield cover 5b is entirely brought into abutment with the outer peripheral portion of the circuit board 2, while a top portion of the shield cover 5b on the opposite side is brought into abutment with an inner wall of the housing 5, thereby pressing the circuit board 2 to the base 4 from above for positioning of the circuit board 2. Part of an edge portion of the shield cover 5b is extended for connecting to the external terminals 3 for grounding therethrough.
A connector portion 5a for connection to an external connector (not shown) is formed at one side of the housing 5. The external terminals 3 are embedded and supported in the center of the connector portion 5a. A pressure introducing passage 7 is formed through the base 4 and connected to the pipe 1b. A filter 7a is disposed midway along the pressure introducing passage 7. To grip the filter 7a from both sides, the base 4 is divided into two members 4a, 4b in the axial direction of the pressure introducing passage 7 (in the vertical direction in FIG. 5). The members 4a, 4b support the filter 7a in place by gripping it from above and below. A portion of the pressure introducing passage 7 formed in the member 4a on the side facing the filter 7a is flared into a conical shape for the purpose of enabling the measured object to pass the filter 7a in a sufficient amount. The pressure introducing passage 7 is air-tightly connected to the pipe 1b with an O-ring 10 fitted over the pipe 1b.
An attachment surface 4c is formed in the base 4 and the pressure sensor device is supported at the attachment surface 4c and attached in a predetermined place. An O-ring 22 is fitted over the attachment surface 4c.
The conventional pressure sensor device having the above-explained structure is attached to an attachment hole 50a bored in a wall of an engine intake system 50, for example, such that the base 4 is inserted in the attachment hole 50a, the attachment surface 4c is engaged with a peripheral edge of the attachment hole 50a, and the boundary between the attachment surface 4c and the attachment hole 50a is sealed by the O-ring 22. After being thus attached, the pressure sensor device measures the pressure in the engine intake system.
Further, FIG. 6 is a view showing the structure of a conventional temperature sensor device disclosed in, e.g., Japanese Unexamined Utility Model Publication No. 4-30448. In FIG. 6, a thermistor 16 used as a heat sensitive element is contained in a holder 15 and sealed by a resin 20 filling the surrounding of the thermistor 16. Two leads 17, 17 are connected to the thermistor 16, and one lead 17 is covered by a tube 13 for insulating the leads 17, 17 from each other. The temperature signal detected by the thermistor 16 is output to the exterior from terminals 25 embedded in a connector 24. A housing 26 supports the holder 15 and the connector 24, and has a threaded portion 26a formed in its outer peripheral surface for attachment of the temperature sensor device to a predetermined position. Between the housing 26 and the holder 15, an O-ring 27 is disposed to seal an object to be measured from the open air.
The conventional temperature sensor device having the above-explained structure is attached to an attachment hole 50b bored in a wall of an engine intake system 50, for example, such that the threaded portion 26a formed in the outer peripheral surface of the housing 26 is fastened into the attachment hole 50b to close it. After being thus attached, the temperature sensor device detects the temperature of the measured object.
Because the conventional pressure sensor device and temperature sensor device are constructed as explained above, separate sensor devices have been necessary to detect the pressure and temperature of the measured object. This has resulted in the problems of requiring individual attachment of the separate sensor devices to the engine intake system 50, for example, to the respective attachment holes 50a, 50b, as well as requiring external connectors and connecting wires specific to the separate sensor devices for supplying electrical power and outputting signals. In addition, external covering parts and internal constituent parts are also required for each of the separate sensor devices. It has been therefore difficult to manufacture the separate sensor devices cost-effectively in total.